Projectile for rifled firearms.



PATENTBD NOV. 26

L. SGHUPMANN. PROJBGTILE FOR RIFLBD FIRBARMS.

APPLIOATION FILED `SEPT. 7.1906.

Figli)- Inventor .ludwglg'hupman'zg LnDWiG senUPMANN, or A Ix-LA-onArELLE, GERMANY.

PROJECTILE non nrFLED FIREARMS.

To all whom it may concern:

Be it known that I, LUDWIG SCHUPMANN, privy counselor and professor in the Royal Iolytechnicum at Aix-la-Chapelle, a subject of the King of Prussia, residing at Aix-la.-ev

Chapelle, No. 18 Mariahilfstrasse, in the Kingdom of Prussia, `Empire of Germany, have invented certain new and useful Improvements Projectiles for Riied l-Firearms; and I do hereby declarelthe following to he a full, clear, and, exact description of,v

the invention, such as will enable others skilled in the art to which it appertains to make anduse the same.

My present invention relates to projectiles and particularly to that class thereof destined for rifled barrels, and it has forlits object to provide the surface of the projectile with helical grooves and thus enable it, when fired from the rifled barrel, to penetrate the air in a less curved line than an ordinary projectile.

In the accompanying drawing z-Figure 1 is aside View of my projectile,in which the dotted lines indicate the impressions or the direction ofthe rifling of the barrel. the following -iigures the direction of the twist of riiling is supposed to be the same as shown in this figure. Fig. 2yis aside view of a similar projectile, in which the helical grooves are running in .the opposite direction to that shown in Fig. 1.-- Fig. 'Sis a rear viewl of the projectile shown'in Fig. 2. Figs..4 and 5 are similar rear views and re resent modifications of the cross-section of t le helical grooves; Figs. 6, 7, 8 and Qshow different arrangements of the helical grooves of my projectile. Fig. 10 is a side 'view diagram which specifically ill strates the effect of the helical grooves upo a iired projectile. Fig. 11 represents the-diagram shown in Fic.' 1() as seen from below. vantageous shape of an elongated small irearm projectile kto'which my invention applies.

Il" it were possible to transform the -paraboloidal path of a fired projectile into a straight line, it would be far easier to hit the mark, as then the knowledge of the distance which lies between the'riileman and the 'tar- Specification ofLetters Patent.

Application filed September 7. 1906. Serial No. 3331592l thisy objection is not maintainable.

crease the inaccuracies of fire In all Fig. 12 shows an a Patented Nov. 2e, 1967.

raised the objection that this urposeseems to involve a physical 4imposslbility, but if considered -that certain toys, for instance the boomerang, accomplish even more by progressing onl a path curved in the opposite way, so that the ascent gradually increases,

Moreover, the store of energy which-an advancin projectile possesses is so great that a small portion of this energy amply suffices to hinder the dropping of said projectile during a given space of time, provided of course, that the means employed are suitable'ones.

Generally-speaking it must beconceded, thatJ any inequalities'pr roughnesses on the exterior of the projectile merely tend to ingrooves with Whichmy 4roje'ctile is'provided run regularly in equal distances aroundthe axis of the projectile and are'proyided with the same profile, so that the center of gravity of each cross-section'of the projectile lies preclisely in the longitudinal axis ofthe project- 1 e.

fluttering movements around this' axis islassured and therefore a precise fire warranted. This same quality-of a free axis a rojectile possesses which is only provided witv the impressions of the rifling, andexperience has butl the For these reasons the longitudinal a'xisl possesses the quality of a so call/ed; free axis, so that a continuous rotation without taught that these projectiles, in spite of their impressions or grooves, warrantla more accurate {irethan projectiles fired from smoothbore barrels'. Consequently the application of grooves, if re ularly arrangedy and if adapted and capa le to serve'lanadvantageous purpose, can produce great advan--f ta es.

` n Fig. 10 the axis A-B of the 'projectile'a which has just left the muzzle coincides `with the tangent A-H to the path of the projectile, which tan ent may besuppo'sedto be horizontal.- Whi e the projectlle advances on its curved path the projectile retains, as is -well known, the direction of its axis C-D unaltered, '11. e. parallel to A--B, because it rapidly spins about its horizontal axis on ac-l count of the twist of the rifling. For this reason the axis C-D of the projectile and the tangent to the path-of the projectile novvr i jectile, though greater than upon the uppersurface thereof, could never suflice to elevate the projectile to the horizontal line A-H, because yonly the .dropping or sinking of the projectile produces this greater'pressure of the a 1rupon the under-surface. But my projectile is provided with said helical grooves. The forces which inA consequence pfthese grooves act upon the flying projectile are the resisting forces of theair which act'ag'ainst these grooves or'rather against their in closures or the ribs which inclose them. The upperpart of the two zones providedwith grooves are free from resistance because they are sheltered by the body of the projectile against'the air, which strikes the projectile from below 'and from in front according to the angle a, Fi 10. ,The lateraliparts of said zones are 'likewise almost free from resistance, because their plane nearly coincides with a line parallel to the celerity of'the projectile. sides-the friction there remain unquestionset of grooves, which are directed upwards and downwardsand equal to each other and merelytend to alter the rotatory celerity of -the projectile, but by far the greatest effect is produced by the under parts of the grooved zones, becausethe resisting air strikes directly against their areas. This effect is proportional to the projection of the groovedarea 'perpendicularly to the celerity of\ the projectile and in consequence, all other things being equal, proportional to the breadth of the zones, to the diameter of the projectile, and to the angle a.

Examining now the eilect of the under parts Of the grooved zones, it must be remembered, that the rotatory celerity of the circumference oi.' the projectile is small in proportionto its'advancing movement, because the riflingis not very inclined. Without committing'a reat error we lcan therefore assume, that t e air will strike the ribs which separate the grooves, under an angle of' about 45o, Vif said grooves are arranged .under this inclination to a line running parallel with the longitudinal axis of the projectile. This error disappears if the grooves 'are -arranged in such a manner, that their inclination forms an angle o'i 45 viith the direction of the riling. The angle a, Fig. 10, is hereby of no importance, because very small'. Dissolving this against the under ribs in the well known manner into its components, We finally Obtain at the front-set of grooves a force which opposes the advancing movement of the projectile, and another almost equal force P, Figs. 1() and 11. At the rear-set of grooves we likewise obtain a force which opposes the advancing movement and the force O, Figs. 10 and 11.

The two forces which act in opposition Of course, be-

ressure of the airl to the advancing movement retard the projectile in its course, but it must be remembered, that the pressure of the air against vthe point of the projectile is so great, that this retardationis of no importance in comparison with the'retardation caused by the pressure of the air against the oint of the projectile. The two remaining orces O and Figs. 1() and 11, form a force-couple which tends to alter the direction of the axis of the projectile horizontally. These forces are essential for my invention, because they greatly change the path of my projectile in comparison with an ordinary projectile. Such cause for deviating the direction of the axis of the proj ectile'ihorizontally would also be produced if' only the front-set of helical'.

grooves, or for that matter the rear-set oi' such helical grooves, existed, because the force P aswell as the force -O does not intersect the center of gravity of the projectile, but then said cause would be only half as effective. From numerous treatises on physics, and also from experiments with the gyrolscope it is known that a spinning body answers to such a force-couple in a remarkable way, in as much as its axis of rotation, is not altered'in the sense of the force-couple but perpendicularly thereto. Consequently in our case, according to Perrys rule (Spinning Tops, London 1890, page 42) the point ofthe projectile will be lifted, while the rear-end will be lowered, so that the axis of the projectile will attain the inclined position E-F shown in Fig. 10. This inclination against the primary tangent A-H, Fig 10, .enables the pressure of the air which acts upon the now inclined under-surface of the projectile, todiminish the distance between the primary tangent andthe pathway so that the proj ect-- ile does not take the path A-L of ordinary projectiles, but will chooseI the straighter path A-K. Only by means of my invenion can be obtained that during the course of the projectile this inclination of its axis to the direction of the primary tangent to the path- Way is produced. Very small inclinai' ions produce forces, especially at the beginning ol the pathway where the celerity is still very great, which are directed upwards perpendicularly to theinclined under-surface of the projectile and which are .great enough lo alter the course of 'the projectile essentially.

' We will assume that the inclination tothe tangent A--IL Fig. 10, amounts for instance to 1 only. It may .he assumed that the projectileunder consideration is a small one, say 3- centimeters in length and 0.7 centimeters in diameter. The area of the undersurface which comes under consideration for the air-pressure is therefore 3X().7=2.1 square centimeters; but taking the cylindrical curvature and the grooved zones into `consideration-this area may be assumed to contain only 1.2 square centiIIictcrs. 'lhe weight of such a projectile is about 13 grams.. According to the Well known formula We have the equation which the air presses the projectile upwards perpendicularly to its inclination, F the area -(1.2 square centimeters) under pressure; and the angle of inclination to the direction of motion. 'llh'e angle /5 is therefore equal to the angle a/-l- 1o. Ve willassume the angle to be =1.` In this manner we obtain only the increasel of the force l), which acts upon my projectile in comparison with an ordinary projectile'. ln the above equation further signifies, fu the celerity of the projectile (about 60,000 centimeters), C a coellcient (about 2), y the weight of the. cubic unit of air (0.0013 grams per. cubic centimeter), and g the acceleration of gravity (981 centimeters). Inserting-these numeral values into theabove equation we'obtaln 1 P=12 lj i 2 Q XQ-Ofll:

1.75 grams nearly question, we would 'have obtained P=100 grams approximately. Theseforces Which we have obtained are therefore able t'o alter the course of thisV projectile essentially, whose Weight is only 13 grams. Besides this We see that science has not yet far enough advanced helical grooves, as shown in Figs. 8 and 9.

lf for instance the rear set of helical grooves is omitted, only the force Pl Fig. 11, will act upon the projectile, which tends not only to twist it, but also to deviate it horizontally, while the counter-balancing force O will be missed. This being so', the choice of-one or theothcr of the arrangements shown in Figs. 2, G, 7, 8 and 9 will form the means to modify the horizontal forces land thus reduce the horizontal deviation, which varies by the lillerent shapes of projectiles as well in direction as in extent.

lhc inclination of Athe helical rooves against the direction of the twist of riiling is Vto vmy projectile, as thereby the air is entheoretically adr'anta eous if chosen to be .about 30o' to 45, w 'le the profile of the helical grooves, if sufficiently deepened, is theoretically of less importance, but the greatest-effect may be; expected, when the ribs d are made as small as possible' in Comparison with the-width of the helical grooves. Besides this the profile'of the projectile may beadapted to suit the practical endsin view. Different profiles appear in therear .70 views given in t e Figs. 3, 4 and "5. The profile shown in Fig. 4 possesses advantages for iron-mantled projectiles, Whereas the profile shown in Fig. 5 promises good results, be-

cause the active small surface e, turned to- "Ward the point of the projectile,l can be reached bythe air With great facility.

Generally speaking, theprojectile is least retarded on its path when the grooves are deepest at the circuits f and g indicated in Fi .2. I

(rdinary small rojectiles are etten provided with a smal ring-shaped groove near their rear end, which groove can be adapted abled to enter easily into the1rear-set of helical' grooves, an arrangement illustrated in Fig. 12.

.It now. remains to demonstrate how the same purpose, i. c. the straightening ofthe path of the projectile, can be obtained, if the helical grooves run around the axis of the projectile in the o posite sense to that shown in Figs. 2, 10 an 11, which arrangement is represented in Fig.` 1.. In, this case the force-couple O--P, Fig. 11, is inverted and now tends'to depress the point of the projectile, so that the angle a, Fig. 10, is gradually diminished. A projectile of this class would consequently fly through the'air like a 100 feathered arrow, t. e. so that the long axis coincides with the direction of the projectile path, wherefore the tilting-over of the projpctile is not to be feared, and it is a well- A nown fact, that this eventuality prohibits the making of Athe point of ordinary projectiles very sharp. We have now a means of sharpening the point of the projectile without any inconvenience, and thus of straightening the path of the projectile, which will become evident by the following state- Ament z--A projectile which advances With its longitudinal axis coinciding with the direction ofthe pathway offers a minimum of resistance to the air, because the projection of .its body-in the direction of the movement is in this position of the sinallestcogitable area.

-In this position the air pressure is on the under surface of the projectileequal to that ofthe upper surface thereof, because both surfaces 11e in the direction of the movement, so that the resistance of the air acts exactly symmetricallyk against the point of the projectile and precisely opposite to the direction -of the pathway. Dlminishing the air-resistance on the one hand by Shar ening the projectile, and on the other hand y this position of the projectile, We obtain advantages so great, that all other circumstances' are 'of secondary nature. The total resistance against the pointed front-end of the above-named projectile of 13 grams weight is according to ourformula about 500 grams. By sharpening the point this Vresistance can be easily reduced to about 250 grams. Thesel great resisting forces grad# ually consume the energy of the projectile, i. e. diminish its velocity. As the curvature of the pathway is nearly inversely proportional to the velocity', we obtain by reducing the resistance to one half a much less curved A pathway than usually. The' projectiles. of

th latter class with inverted grooves oHer moreover the advantages that-the'so called Ahorizontal deviation is annulled, and that 1. A pointed projectile having its forward` cylindric part provided With a set of helical jectile is to be. used, to alter by the effect of said grooves the inclination of the longitudinal axis of the projectile to the horizontal plane during the course of theprojectile.

2. A pointed projectile having its forward cylindric part provided with a set oihelical grooves, its body to the rear of such part not provided with said rooves and adapted to itthe riiled bore o? the gun in which the projectile is` to be used, and at or near its rearV end provided with a' set of helical grooves, to alter by the effect of said grooves the inclination of the longitudinal axis of the projectile to the horizontal plane during the course of the projectile.

. In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

LUDWIG SCHUPMANN. Witnesses WILLIAM J. REUTERS, HENRY QUADFLIEG. 

